This invention relates to a mobile telephone device provided with a transmitter and a receiver which may each comprise a high-frequency component.
A mobile telephone device comprises, besides a loudspeaker, a display device, and means for the supply of power, also a transmitter with a high-frequency component and a receiver with a high-frequency component for the purpose of receiving and transmitting data.
The mobile telephone device comprises not only a high-frequency circuit but also a DC source which is to be decoupled from the high-frequency signals.
Capacitors, so-called decoupling capacitors, are used for decoupling. The function of a decoupling capacitor is to attenuate the undesirable high-frequency signals so as to safeguard a constant DC power supply to the components of the high-frequency circuit.
To obtain decoupling over a wide frequency range, decoupling capacitors are required which have a high C/L (capacitance/inductance) ratio, i.e. with high capacitance values and low inductance values. In an ideal case, all undesirable high-frequency signals are smoothed out by such capacitors. Although discrete capacitors with low inductance values can be manufactured nowadays, inductance values of 400 pH for capacitors of the type 0402 and 300 pH for capacitors of the type 0201 are so high that it is only possible to use capacitors with capacitance values of a few pF. Only a narrow frequency range can be decoupled by means of such a decoupling capacitor. For this reason, several discrete capacitors with different capacitance values are provided on the substrate on which the high-frequency circuit and the DC source are present for decoupling a wide frequency range. Capacitors of low capacitance are thus used for decoupling higher frequencies and capacitors of high capacitance for decoupling the lower frequencies.
The use and mounting of several discrete decoupling capacitors is not only expensive, but the discrete decoupling capacitors also occupy much space on the substrate.
A decoupling capacitor is known from U.S. Pat. No. 6,038,122, of which one electrode has a tapering shape, for example a triangular or fan shape. This special electrode design gives the capacitor varying capacitance values between its two connection terminals, and the different frequencies are decoupled in different regions of the decoupling capacitor. It is an advantage of this decoupling capacitor that only one discrete component is to be mounted. A disadvantage of this decoupling capacitor is that it is very complicated and expensive in manufacture because of the special electrode structure.
The invention has for its object to provide a mobile telephone device fitted with a transmitter and a receiver, which may each comprise a high-frequency component with a decoupling capacitor, wherein the decoupling capacitor effects a decoupling over a wide frequency range and is simple to manufacture.
This object is achieved by means of a mobile telephone device provided with a transmitter and a receiver, which may each comprise a high-frequency integrated circuit component, wherein the high-frequency component comprises a high-frequency circuit, a DC source, and a decoupling capacitor all integrated together on a common substrate, wherein the decoupling capacitor comprises a first electrode, a dielectric, a second electrode, and a first and a second current supply terminal on one and the same side of the decoupling capacitor, and wherein one electrode is connected to the high-frequency circuit and the DC source and the other electrode is connected to ground.
It is possible to create a decoupling capacitor of low inductance value in the mobile telephone device through the direct integration of the decoupling capacitor on the substrate with the high-frequency circuit, because very small electrode dimensions are possible. As a result, the C/L ratio of the decoupling capacitor can be increased. In addition, a decoupling capacitor can be manufactured in which the current supply terminals lie on the same side of the decoupling capacitor, owing to the integration. A contacting of the electrodes on the same side of the capacitor means that the current flows in opposite directions through the electrodes, and the magnetic fields occurring in the decoupling capacitor and defining the self-induction are clearly reduced. The C/L ratio of the decoupling capacitor is increased thereby. The provision of the current supply terminals on one side is also referred to as the counter-current principle.
The improved C/L ratio of the decoupling capacitor means that only one decoupling capacitor is required for decoupling a wide frequency band.
A further advantage of the mobile telephone device is that the external dimensions of an integrated decoupling capacitor are smaller, so that smaller high-frequency components can be manufactured. In total this renders possible a further miniaturization of the mobile telephone device. Furthermore, an expensive mounting of discrete decoupling capacitors on the high-frequency component becomes redundant.
The invention further relates to a high-frequency component which comprises a high-frequency circuit, a DC source, and an integrated decoupling capacitor on a common substrate, wherein the decoupling capacitor comprises a first electrode, a dielectric, a second electrode, and a first and a second current supply terminal on one and the same side of the decoupling capacitor, and wherein one electrode is connected to the high-frequency circuit and the DC source and the other electrode is connected to ground.
Preferably, the decoupling capacitor is constructed by means of thin-film technology.
The C/L ratio of a decoupling capacitor can be influenced by means of thin film processes. In a thin-film process, a decoupling capacitor can be realized whose dielectric has a smaller layer thickness d (d less than 1 xcexcm), and which accordingly has a higher capacitance density. The resulting decoupling capacitor has a higher value for its C/L ratio.
It is particularly preferred that a further integrated passive component is provided on the substrate.
Further integrated passive components such as, for example, a coil, a resistor, or a capacitor may be provided directly on the substrate through a suitable structuring of the electrodes and the dielectric of the decoupling capacitor or through the deposition of further functional layers. As a result, the mounting of further discrete components which are to be present on the high-frequency component is avoided, and a further miniaturization of the mobile telephone device is rendered possible.
It is advantageous when the high-frequency circuit is an amplifier circuit, a mixer stage, or a voltage-controlled oscillator.
An effective decoupling of undesirable high-frequency signals is necessary in all these high-frequency circuits.